The present invention generally relates to wood chip production and specifically to a power transmission for a material stripping or delimbing apparatus and to the removal of debris which typically accumulates between the material stripping apparatus and a material chipping apparatus at a chip production site.
In wood chip production, a chip production site typically includes a material stripping apparatus for removal of limbs and bark, and a material chipping apparatus for chip production from the delimbed and debarked trees. There apparatus will typically be set up in an area of forest where trees will be cut down for chip production. The stripper and chipper will commonly be arranged with respect to each other so that material will feed directly into the chipper from the stripper. A semitrailer is usually positioned adjacent the chipper for receiving finished chips.
The stripper removes limbs, bark, and dirt or the like from trees to improve the quality of the chips produced. This debris, removed by the stripper, is typically discarded. While many strippers provide for removal of the debris from the stripper, the debris typically accumulates between the stripper and chipper and is commonly carried out of the stripper by the flow of the stripped material itself. Thus, the stripper and chipper will typically be spaced approximately five feet apart so that debris can fall from the flow path of material before entering the chipper.
A common type of stripper is the chain flail delimber which uses rotating stripping elements having a series of chain lengths, rotating about a drive shaft, to flail passing material and remove limbs, bark, dirt and debris prior to chipping. However, lengths or portions of the flail chains sometimes break off and are carried out of the stripper with the material. Thus, another reason for providing a gap between the stripper and chipper is to allow these chain portions to fall from the trees prior to entering the chipper. If these chain portions enter the chipper, damage to the chipper may occur and significant repair to the chipper is required. This results in costly down time for the production facilities as well as labor and material costs directly for the repair.
A common procedure for operation at a chip production site is to use a tow vehicle or skidder to drag cut trees out of the forest to the infeed side of the stripper. A crane device is used to pick up and feed the trees or material into the stripper, which will typically have a material transfer device for moving material through the stripper. As indicated above, the material will exit the stripper, carrying a variety of debris, generated by the stripping process, and enter the chipper. As production continues, debris accumulates between the stripper and chipper which is periodically removed by the skidder and is typically dispersed in the forest as the skidder goes to get another load of material. However, because the debris between the stripper and the chipper is not continuously removed and because effective removal of this debris with the skidder is difficult, the debris will typically accumulate between the stripper and chipper to the point where debris carried out of the stripper can not fall from the material and is carried into the chipper.
When debris is fed into the chipper, the debris intermixes with the chips and poor quality chips are produced. Also, portions of chain can be carried into the chipper where they will damage the chipper, specifically the chipper knives, requiring additional maintenance of the chipper and reducing production. Further, requiring the skidder operator to clear debris from between the stripper and chipper distracts the skidder from its primary function of conveying cut trees from the forest to the production site and decreases the efficiency of the production operation.
Another problem in chip production arises from the common use of hydraulic power transmission between the operating engine for the stripper and the stripping elements, commonly rotating flails. While hydraulic pumps and motors provide convenient and flexible power transmission for the large amount of power required to drive the stripping elements, especially as compared to the complexities of shaft drives, hydraulic transmission of such large quantities of power generates commensurate amounts of heat. Since chipping operations are conducted during the summer months of the year and quite frequently in the southern regions in the country, the heat generation of hydraulic power transmission frequently causes overheating of the powering system, requiring frequent shut downs while the heat dissipates and the power system cools. More importantly, such overheating typically damages the hydraulic transmission system and results in significant additional maintenance and repair costs.
Further, there are significant transmission losses in converting engine power to hydraulic power and then converting the hydraulic power to the rotary motion of the flails. When viewed in light of historically escalating fuel costs and environmental concerns regarding the consumption of fossil fuel, an increase in power transmission efficiency between the engine and the stripping element is readily seen to have significant advantages.